The present disclosure relates to a painting installation for the serial painting of components, e.g., of motor vehicle bodies.
Known painting installations for the serial painting of motor vehicle bodies generally measure layer thickness of the paint applied in a measuring cabin during a painting operation continuously (“on-line”). Contactlessly operating layer thickness measuring devices are used for this purpose, which are based on a photothermic principle that is described in DE 195 20 788 C2, for example. These known layer thickness measuring devices irradiate the surface of the motor vehicle bodies to be measured in the measuring cabin with a laser beam in the non-visible wavelength range in a punctiform manner, as a result of, which energy is supplied to the paint layer, which is converted into long-wave heat radiation and is detected by a radiation detector. The layer thickness can then be derived from the reflected radiation.
Initially disadvantageous in this known type of layer thickness measurement is the fact that the measurement only takes place in a punctiform manner, so that a plurality of individual measurements is required for a two-dimensional measurement of the layer thickness over an area. So, currently, for every motor vehicle body, the layer thickness of the paint applied is measured at 60-100 measurement points, which are distributed over the motor vehicle body. The plurality of the required individual measurements requires a certain minimum cabin length of the measuring cabin for a predetermined measuring duration of the individual measurements and a likewise predetermined cycle time of the painting installation, cabin lengths of 5 to 7 metres being required in some cases, which makes the subsequent integration of measuring cabins of this type into an existing painting installation more difficult.
A further disadvantage of the previously described known layer thickness measurement consists in the fact that, on account of the required energy density, lasers must be used, which are dangerous for eyes and skin in the case of a certain combination of irradiated power, wavelength and divergence of the laser beam. Particularly in the case of laser radiation in the non-visible wavelength range, there is a danger for the human eye, as the eye cannot then perceive the laser radiation. In the known painting installations with this layer thickness measurement, the measuring cabin must therefore have a certain minimum cabin length in order to prevent the laser beam from being able to leave the measuring cabin.
In the case of the known layer thickness measurement, a relatively large cabin length of the measuring cabin is therefore required for various reasons, which makes a subsequent integration into an existing painting installation more difficult or may even prevent installation entirely.
A painting installation for the painting of motor vehicle body components is known from U.S. Pat. No. 7,220,966 B2, where motor vehicle body components are cured in an infra-red oven after painting and are subsequently measured by an infra-red sensor, in order to detect painting defects. This known measurement method does not make it possible, however, or only makes it possible to an unsatisfactory degree to determine the layer thickness of a paint.
Further, for the prior art, DE 10 2006 009 912 A1, DE 197 49 984 C2, “Impuls-Thermographie”, Fraunhofer Allianz Vision, in the version of 14 Jun. 2007, DE 195 20 788 C2, EP 1 749 584 A1, GB 2 367 773 A, DE 195 17 494 C2, U.S. Pat. No. 5,598,099 A and DE 197 56 467 A1 are to be pointed out.
Accordingly, there is a need in the art for an improved painting installations with a more effective layer thickness measurement. Additionally, it is desirable to reduce the minimum cabin length of the measuring cabin, so that the measuring cabin or measuring cell can also be integrated subsequently into an existing painting installation.
The exemplary illustrations generally comprise the general technical teaching of carrying out the layer thickness measurement in a painting installation in a novel manner, in order to enable a reduction of the required cabin or zone length of the measuring cabin or measuring zone. So, instead of the above-described punctiform irradiation of the component surface to be measured with laser radiation in the non-visible wavelength range, the exemplary illustrations provide that the component surfaces to be measured may be irradiated and measured in a flat (2 dimensional) manner. This offers the advantage that the number of the individual measurements required is reduced, which in turn enables a shortening of the measuring cell and, as a result, facilitates an integration of the measuring cell into an existing painting installation.
In one illustration, the component surface to be measured is irradiated in the visible wavelength range, wherefore flashguns or gas discharge lamps can be used for example. The excitation of the component surface to be measured does not necessarily however have to take place by means of light, but rather can take place generally with radiation. Possible radiation sources are ultrasound transmitters, light sources, flashed light sources or light emitting diodes (LEDs), which emit non-dangerous light with regards to energy density and wavelength.
Furthermore, the radiation excitation of the surface to be measured can optionally take place in the form of individual pulses, pulse sequences, in a modulated manner or continuous manner.
On the one hand, the irradiation of the component surfaces to be measured with visible light offers the advantage that there is no health hazard as long as the radiated power is low and the wavelength is configured in such a manner that conventional glass panes lead to absorption, so that the measuring cell can turn out shorter, as no measures are required in order to prevent an escape of the hazardous laser radiation.
On the other hand, the irradiation by means of a flashgun or a gas discharge lamp has the already-mentioned advantage that the irradiation of the component surfaces to be measured takes place in a flat (two dimensional) manner, so that in the context of a single measurement, the layer thickness is not only measured in a punctiform manner, but rather over a certain measurement area. As a result of this, the number of the individual measurements required is reduced, which in turn enables a shortening of the measuring cell and, as a result, facilitates an integration of the measuring cell into an existing painting installation.
The exemplary illustrations are not limited to a certain size of the measurement area, however it is to be mentioned that the measurement area may in some examples be larger than 10 cm2, 50 cm2, 100 cm2, 250 cm2, 500 cm2, 1000 cm2, 1 m2 or 2 m2. The term measurement area used in the context of the exemplary illustrations means that the layer thickness within the measurement area can be determined two dimensionally in a single measurement procedure.
In the case of a measurement by means of an infra-red camera, the layer thickness is measured in each pixel of the infra-red camera. This produces many layer thickness values for each measurement, in accordance with the number of pixels of the infra-red camera. Furthermore, it is also possible to average locally over of a plurality of pixels.
In the case of the exemplary painting installations, the measuring cell may advantageously include a flashgun or a gas discharge lamp as radiation source or excitation source and may include an infra-red camera as radiation detector. The radiation detector may have a wide-angle measuring sensitivity and measure the surface of the painted components in a flat (two dimensional) manner within the respective measurement area.
In an exemplary illustration, the radiation source and/or the radiation detector are arranged in the measuring cell on a portal machine, which spans the transport path, it being possible to arrange the portal machine optionally such that it can move along the transport path or such that it is stationary.
In another exemplary illustration, the radiation source and/or the radiation detector are by contrast arranged in the measuring cell on a stand, the stand optionally being arranged such that it can move along the transport path or such that it is stationary.
Particularly advantageous in the exemplary painting installation is the fact that the measuring cell only requires a relatively small zone length along the transport path, which is generally smaller that the zone length of the painting cell. For example, the zone length of the measuring cell can be smaller than 7 m, 5 m, 3 m, 2 m or 1 m to mention a few limit values, merely as examples.
In an exemplary illustration, a guide for the radiation detector and/or for the radiation source is arranged in the measuring cell, so that the radiation detector and/or the radiation source can take up various relative positions in the vertical and/or lateral direction with respect to the painted components. This movable arrangement of the radiation detector and/or the radiation source makes it possible that only a single radiation detector and/or a single radiation source is arranged in the measuring cell. For measuring the various component surfaces (e.g. roof areas, side areas) of the components to be measured, the radiation detector and/or the radiation source may then be brought into a suitable relative position within the measuring cell relatively to the component to be measured.
In another exemplary illustration, the radiation detector by contrast allows the measurement of a plurality of part areas of the components, which are at an angle with respect to one another, from a predetermined position. For example, the radiation detector in this exemplary embodiment can measure both a side area and the roof and bonnet areas from one position. This enables a complete measurement of the painted components with only two radiation detectors and radiation sources, which are arranged within the measuring cell at suitable positions. Here also, a guide can be provided in order to position the radiation detectors and/or the radiation sources within the measuring cell in the lateral and/or vertical direction.
In a further exemplary illustration, three radiation detectors and/or three radiation sources are by contrast provided in the measuring cell, which may be arranged in a stationary manner in the vertical and lateral direction with respect to the components. Here, two of the radiation detectors and/or two of the radiation sources may be arranged laterally next to the transport path on opposite sides and measure the two side areas of the painted components. One of the radiation detectors and/or one of the radiation sources may, by contrast, be arranged over the transport path and measure the horizontal areas of the painted components, such as for example the roof areas and the bonnet areas of motor vehicle bodies.
In the case of the previously described exemplary illustrations, the portal machine, the stand and/or the guide for the radiation sources or radiation detectors can be moved along the transport path, for example a controllable displacement device can be provided. In the case of a continuous transporting of the painted components by means of the measuring cell, the displacement device may then be, for example, by a system control of the painting installation in such a manner that the radiation sources or radiation detectors move through the measuring cell synchronously to the painted components, in order to prevent a relative movement between the painted components on the one hand and the radiation detectors or radiation sources on the other hand during the measurement procedure.
Alternatively, however, there is also the possibility that the radiation sources or radiation detectors in the measuring cell cannot be moved along the transport path. In the case of a continuous transporting of the painted components through the measuring cell, the relative movement between the painted components on the one hand and the radiation detectors or radiation sources on the other hand may then be subtracted by an image processing computer, in order to enable a meaningful measurement.
Furthermore, there is also the possibility that the radiation detector (e.g. infra-red camera) can measure so quickly that a compensation of the relative movement by means of coupled motion or by means of image processing is unnecessary.
In the case of the irradiation of the painted surfaces by means of a flashgun or a gas discharge lamp, there is the possibility that a fire sensor arranged in the painting installation reacts to the irradiation so that a fire may potentially be erroneously detected. It may therefore be possible to block a fire detection as long as the radiation source is irradiating the painted components for measurement purposes. The painting installation according to the exemplary illustrations can therefore have a fire protection system with at least one fire sensor, at least one extinguishing device and a first control unit, the first control unit being connected at the input side to the fire sensor in order to detect a fire, whilst the first control unit is connected at the output side to the extinguishing device, in order to activate the extinguishing device. The first control unit here detects whether the radiation source irradiates the painted components and blocks the activation of the extinguishing device independently of the signal of the fire sensor as long as the radiation source irradiates the painted components.
Furthermore, the measuring cell in the exemplary painting installation may have an inlet and an outlet, the painted components being transported on the transport path via the inlet into the measuring path and via the outlet out of the measuring cell. It is advantageous here that the inlet and/or the outlet of the measuring cell have a changeable opening cross section, in order to adapt the opening cross section to the actual changeable cross section of the painted components. On the one hand, the cross section adaptation takes place in such a manner that the painted components are not contacted when passing through the inlet or the outlet. On the other hand, the controlling of the opening cross section takes place in such a manner that a minimum clear gap remains between the opening cross section and the outer contour of the respective component. This is advantageous in order to prevent an escaping of the radiation out of the measuring cell, as flashed light for example is disruptive and could activate fire sensors outside of the measuring cell.
The measuring cell therefore may have an infeed device, which sets the opening cross section of the inlet and/or the outlet of the measuring cell in accordance with the actual cross section of the painted components, the infeed device being controlled by a second control unit in accordance with the predetermined cross section of the painted components.
The actual cross section or the actual outer contour of the components running in or out can for example be determined, for example, by one or a plurality of distance sensors or by a so-called light array, this being a plurality of light barriers, which are arranged at right angles to one another. A combination of light barriers and distance sensors is likewise conceivable.
Alternatively, in the context of the exemplary illustrations, there is also the possibility that the actual cross section of the components running in or running out is communicated by a system control.
Further, in the context of the exemplary illustrations, there is also the possibility that the measuring cell has a rolling shutter gate at the inlet and/or outlet side, in order to close the measuring cell during a measurement procedure.
Further, it is advantageous if the radiation source has a screen, which limits the radiation onto the component surface to be measured, it being possible for the screen to have reflective inner areas in order to focus the radiation onto the measurement area.
In the exemplary painting installations, a plurality of painting cells can be arranged along the transport path one downstream of the other, which painting cells apply several paint layers lying one above the other onto the individual components one after another. Here, one measuring cell for layer thickness measurement can in each case be arranged downstream of each of the painting cells, so that the layer thicknesses of the individual paint layers can be determined. The individual layer thicknesses cannot generally be determined independently of one another however, which also applies if measuring is carried out after each individual paint application. The measuring system therefore generally always measures the overall layer of the paint layers applied. From the overall thicknesses measured, the layer thickness of the individual paint layers can then be calculated.
Alternatively, there is also the possibility of using a measuring cell with a layer thickness measuring device, which can selectively measure the individual layers of a multi-layer coating structure. In this case, it is sufficient if a single measuring cell is arranged at the end of the painting process, that is to say in the conveying direction downstream of all of the painting cells. This does not prevent the use of a plurality of measuring stations as well, however, in order to be able to react more quickly to defects in the painting process.
Furthermore, it is possible in the context of the exemplary illustrations that the layer thickness determined is used as a controlled variable in a control loop, in order to correspondingly re-adjust the application control and thus to ensure a layer thickness, which is as constant as possible.
Other advantageous aspects of the exemplary illustrations are explained in more detail together with the description of the various exemplary illustrations on the basis of the drawings.
FIG. 1 shows a schematic, strongly simplified illustration of an exemplary painting installation with two painting cells 1, 2, arranged along a transport path 3, with one downstream of the other, one measuring cell 4, 5 for layer thickness measurement in each case being arranged downstream of each of the two painting cells 1, 2. The measuring cell 4 therefore measures the layer thickness of the paint layer applied by the painting cell 1, whereas the measuring cell 5 measures the layer thickness of the paint layer applied by the painting cell 2.
Motor vehicle bodies 6, 7 may be transported through the painting installation on the transport path 3, it being possible for the transporting to take place continuously or in a “stop-and-go” operation. In the case of a “stop-and-go” operation, the individual painting cells 1, 2 may accommodate the complete motor vehicle bodies 6, 7 in each case.
A plurality of multi-axial painting robots 8-11 or 12-15 may be arranged in the two painting cells 1, 2. The painting robots 8-11 or 12-15 may be movable along the transport path 3 on travel rails 16-19, and may include any type of painting robot that is convenient.
A portal machine 16, 17 may be located in the measuring cells 4, 5 in each case, which spans the transport path 3 and can be moved on transport rails 18, 19 or 20, 21 along the transport path 3.
From the cross-sectional view in FIG. 2, it can be seen that the portal machine 16 in all carries three layer thickness measuring devices 22-24, in order to measure the layer thickness of the paint applied onto the motor vehicle body 7.
The layer thickness measuring devices 22 and 24 are here attached to upwardly projecting posts of the portal machine 16 on the inside and measure the layer thickness on the side areas of the motor vehicle body 7.
The layer thickness measuring device 23 is, by contrast, attached over the transport path 3 above the motor vehicle body 7 to be measured and measures the roof areas and bonnet areas of the motor vehicle body 7 from above.
The individual layer thickness measuring devices 22-24 may contain, for example, a radiation source such as a flashgun in each case, and radiation detector, such as an infra-red camera, in each case, which may measure the body 7 in a wide-angled manner and over a large area and deliver a two-dimensional layer thickness image.
FIG. 3 shows a cross-sectional view of an alternative exemplary embodiment of the portal machine 16, this exemplary embodiment to some extent tallying with the previously described exemplary embodiment, so that to avoid repetitions, reference is made to the previous description and the same reference numbers are used.
A peculiarity of this exemplary embodiment consists in the fact that the layer thickness measuring device 23 is the only layer thickness measuring device, it being possible to guide the layer thickness measuring device 23 in an arcuate manner along the portal machine 16 around the motor vehicle body 7 to be measured, in order to measure the motor vehicle body 7 from various perspectives. In the position shown in FIG. 3, the layer thickness measuring device 23 for example measures the roof areas and the bonnet areas of the motor vehicle body 7.
For measuring the side areas of the motor vehicle body 7, the layer thickness measuring device 23 is by contrast guided along the arcuate portal machine 16 to the side of the motor vehicle body 7.
FIG. 4 shows a further exemplary embodiment of the portal machine 16, which to some extent tallies with the previously described exemplary embodiments, so that to avoid repetitions, reference is made to the previous description, the same reference numbers being used in the following for corresponding details.
A peculiarity of this exemplary embodiment consists in the fact that the two layer thickness measuring devices 22, 23 are in each case arranged at the two opposite upper corners of the portal machine 16, so that the two layer thickness measuring devices 22 can in each case measure the roof and bonnet areas and the respectively facing side area of the motor vehicle body 7.
Common to the exemplary illustrations provided herein is the fact that the portal machine 16 may be moved on the guide rails 18, 19 along the transport path 3 during a measurement in synchronized movement with the motor vehicle body 7 to be measured, so that the layer thickness measuring devices 22-24 on the one hand and the motor vehicle body 7 to be measured on the other hand may maintain a constant relative position to one another along the transport path 3. This may advantageously increase the accuracy of a measurement of a coating layer thickness.
The FIGS. 5A and 5B show the inlet of the measuring cell 5. It can be seen therefrom that a so-called light array is arranged in the inlet of the measuring cell 5, which consists of horizontally running light barriers 25 and vertically running light barriers 26 and determines a cross section or a contour of the motor vehicle body 7 to be measured.
The opening cross section of the inlet of the measuring cell 5 may then be set as a function of the determined contour of the motor vehicle body 7 running in such a manner that, on the one hand, a contacting of the painted motor vehicle body 7 is avoided, but, on the other hand, the remaining clear gap between the opening cross section of the inlet and the outer contour of the motor vehicle body 7 running in is as small as possible. This makes sense, so that substantially no disruptive flashed light escapes from the measuring cell 5.
The inlet of the measuring cell 5 therefore may include a plurality of curtain elements 27, which can be lowered in the arrow direction independently of one another, in order to achieve the desired cross-sectional adaptation of the inlet.
FIG. 6 shows an exemplary control loop with one of the layer thickness measuring devices 22-24, which measures an actual value dACT of the paint layer on the motor vehicle body 6 or 7.
The actual value dACT may be supplied to a subtractor 28, which determines an actual/target-deviation Δd by comparing the actual value dACT with a predetermined set value dSET of the layer thickness.
The deviation Δd is then supplied to a controller 29, which controls an application control 30 as a function of the variance, in order to achieve maintenance of the predetermined set value dSET of the layer thickness, which is as constant as possible.
Furthermore, the set value dACT and the deviation Δd may be supplied to a warning alarm 31, which emits a warning signal if the deviation Δd becomes too large. Here, the predetermined set value dSET is also taken into account, as the warning alarm 31 emits a warning signal if the deviation Δd exceeds a predetermined percentage value of the set value dSET.
Finally, FIG. 7 shows a fire extinguishing device schematically and in a strongly simplified manner, which can be integrated into the measuring cells 4, 5.
The fire extinguishing device consists of at least one fire sensor 32, at least one extinguishing device 33 and a control unit 34. The control unit may control the extinguishing device 33 as a function of the output signal of the fire sensor.
Here, a flashgun 35 may be switched on by a switch-on signal during the layer thickness measurement. Problematic here is the fact that the radiation emitted by the flashgun 35 can lead to a false triggering of the fire sensor 32, which may be undesirable. The switch-on signal for the flashgun 35 is therefore also supplied to the control unit 34, which, during the switch-on time of the flashgun 35, blocks an activation of the extinguishing device 33.
For this purpose, the control unit 34 has a hold element 36 at the input side, the hold element 36 holding the switch-on signal for the flashgun 35 at the output side until the radiated power output has faded away to such an extent that a false triggering of the fire sensor 32 is reliably excluded. The output signal of the holding element 36 may then be passed via an inverter 37 to an AND element 38, which is also controlled at the input side by the fire sensor 32. The control unit 34 only activates the extinguishing device 33 if the fire sensor 32 detects a fire and if, at the same time, the inverter 37 delivers a low level to the AND element 38, which is only the case if there is no danger of false triggering by means of the flashgun 35.
The exemplary illustrations are not limited to the specific examples illustrated above. Rather, a plurality of variations and alterations are possible that also make use of the ideas described herein, and therefore fall within the scope of protection. Reference in the specification to “one example,” “an example,” “one embodiment,” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example. The phrase “in one example” in various places in the specification does not necessarily refer to the same example each time it appears.
With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain embodiments, and should in no way be construed so as to limit the claimed invention.
Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be evident upon reading the above description. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims.
All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “the,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.